For registering measured variables of flowing media, for example, of gases and/or liquids, and for producing measured values correspondingly representing the measured variable, there are used in industrial process measurements technology, especially also in connection with automating chemical processes or procedures for producing a product from a raw or starting material by the use of chemical, physical or biological processes, process-near measuring systems, which are formed by means of: a measuring transducer in communication with a process line carrying the particular fluid, for example, a process line in the form of a pipeline, thus one flowed-through by the fluid during operation, for example, a measuring transducer in the form of a magnetically inductive measuring transducer or a measuring transducer of the vibration-type; as well as measuring electronics electrically coupled with the measuring transducer, in given cases, also remotely therefrom. The measured variable to be registered can be, for example, a density, a flow velocity, a volume flow, a mass flow, or a viscosity of the medium. Examples of such measuring transducers for flowing media, for instance, magnetically inductive measuring transducers or measuring transducers of the vibration-type, or measuring systems formed therewith, are described in, among others, EP-A 045 646, EP-A 1 001 254, EP-A 770 856, U.S. Pat. No. 5,301,557, U.S. Pat. No. 5,796,011, U.S. Pat. No. 6,044,715, U.S. Pat. No. B 6,711,958, U.S. Pat. No. B 6,776,052, U.S. Pat. No. B 6,957,587, U.S. Pat. No. B 7,017,424, U.S. Pat. No. B 7,392,709, WO-A 00/57 141, WO-A 00/57141, WO-A 01/65213, WO-A 03/021202, WO-A 03/021203, WO-A 03/076879 or WO-A 98/38479.
Conventional measuring transducers for flowing media, not least of all magnetically inductive measuring transducers or measuring transducers of the vibration-type, are most often implemented as prefabricated and earlier calibrated, structural units having a measuring tube insertable into the course of the respective process line, serving as part of a physical to electrical transducer, flowed-through during operation of the measuring system by the medium to be measured and equipped with at least one sensor element mounted thereon as well as a transducer housing mechanically coupled with the at least one measuring tube manufactured, for example, of metal. The transducer housing serves as outer protection for the physical to electrical transducer, and is manufactured most often also of metal and forms a cavity accommodating the at least one measuring tube. In the case of a measuring transducer of the vibration-type, the at least one measuring tube is most often held oscillatably at in- and, respectively, outlet-side ends of the transducer housing formed by means of a thick-walled, especially tubular and/or beam-like, support cylinder or a framework, and, for producing mechanical reaction forces in the medium conveyed in the measuring tube, excited, at least at times, to vibrate about a static rest position by means of at least one oscillation exciter, most often an electrodynamic, oscillation exciter, in interactive connection with said measuring tube. For registering, especially inlet-side, respectively outlet-side, vibrations of the measuring tube and for producing at least one measurement signal representing these, such measuring transducers of vibration-type have, furthermore, in each case, at least one oscillation sensor, likewise most often an electrodynamic oscillation sensor, reacting to vibrations, especially bending oscillations, of the measuring tube.
For further processing or evaluation of measuring signals produced by means of the measuring transducer, such includes, furthermore, at least one measuring electronics. The measuring electronics, communicating in suitable manner with the respective sensor element, consequently with the measuring transducer, produces, during operation, from the at least one measurement signal, repeatedly, at least one measured value instantaneously representing the measured variable, for example, thus a mass flow, measured value, volume flow, measured value, density, measured value, and/or viscosity, measured value. For accommodating the measuring electronics, such measuring systems include, most often, a corresponding electronics housing, which can, for example, be arranged remotely from the measuring transducer and connected with this only via a flexible cable. Alternatively thereto, the electronics housing can, as shown, for example, also in the initially mentioned U.S. Pat. No. 5,796,011, be affixed directly on the measuring transducer housing, and so form a compact in-line measuring device. In the case of measuring systems of the described type, the measuring electronics is usually additionally electrically connected via corresponding electrical lines and/or wirelessly via a radio linkage to a superordinated electronic data processing system most often arranged spatially removed from the measuring electronics. Most often, the electronic data processing system is also spatially distributed. Measured values produced by the respective measuring system are forwarded near in time by means of a measured value signal correspondingly carrying the measured values. Measuring systems of the described type are additionally usually connected with one another by means of a line- or radio-based, data transmission network provided within the superordinated data processing system and/or with corresponding electronic process controls, for example, on-site programmable logic controllers (PLCs) or process control computers installed in a remote control room, where the measured values produced by means of the measuring system and digitized and correspondingly coded in suitable manner are forwarded. By means of process control computers, using correspondingly installed software components, the transmitted measured values can be further processed and visualized as corresponding measurement results e.g. on monitors and/or converted into control signals for other field devices embodied as actuating devices, such as e.g. magnetically operated valves, electric-motors, etc. Accordingly, the data processing system serves usually also, to condition the measured value signal delivered by the measuring electronics in accordance with the requirements of downstream data transmission networks, for example, suitably to digitize the measured value signal and, in given cases, to convert such into a corresponding telegram, and/or to evaluate such on-site. For this purpose, there are provided in the data processing systems, electrically coupled with respective connecting lines, evaluating circuits, which pre- and/or further-process as well as, in case required, suitably convert the measured values received from the respective measuring electronics. Serving for data transmission in such industrial data processing systems are at least sectional, especially serial, fieldbusses, such as e.g., FOUNDATION FIELDBUS, CAN, CAN-OPEN, RACKBUS-RS 485, PROFIBUS, etc., or, for example, also networks based on the ETHERNET standard, as well as the corresponding, most often application comprehensively standardized, transmission protocols.
The transducer housing serves, besides for holding the at least one measuring tube placed within the cavity formed by the transducer housing, especially, also for protecting the exciter—and the sensor arrangement, as well as other internally lying components, against outer environmental influences, such as e.g. dust or water spray, consequently to provide a cavity sealed as hermetically as possible. Frequently, moreover, the user also requires that the housing for the measuring transducer, in the case of an unsealed or burst measuring tube, can retain the static internal pressure, which then most often clearly lies above the atmospheric, external pressure, within the cavity, leak-freely, at least for a specified amount of time. Thus, the housing should have a certain level of pressure resistance; compare, in this connection, also the initially mentioned WO-A 00/57 141, U.S. Pat. No. B 7,392,709, U.S. Pat. No. B 6,957,587, U.S. Pat. No. 6,044,715, U.S. Pat. No. 5,301,557, or EP-A 1 001 254. Particularly for applications with toxic or easily flammable fluids, the transducer housing must, in given cases, even be able to meet the requirements placed on safety containers.
A disadvantage of the state of the art associated therewith is that, not least of all also for applications with media under high static pressure of far above 100 bar, in the case of corresponding scaling of conventional transducer housings, the particular wall thickness and, associated therewith, the mass as well as the manufacturing costs increase disproportionately.